Characterization of Green and Ultraviolet LEDs by Laser-Based FA Techniques

This work modifies existing nondestructive, laser-based techniques, such as thermally-induced voltage alteration (TIVA) and light-induced voltage alteration (LIVA), to determine precursors to failure in green and UV LEDs. Both TIVA and LIVA have been shown to be effective tools in localizing defects in Si-based integrated circuits and GaAs vertical cavity surface-emitting lasers. In a previous work, TIVA was also used to demonstrate failed InGaN LEDs in the III-V material system. This article expands the use of these techniques to localize potential precursors that lead to premature failures in deep green and deep UV LEDs. The paper shows how the TIVA/LIVA techniques were successfully used to characterize defects in wide bandgap AlGaN- and InGaN-based LEDs. The defects in the green LEDs appear to be electron-hole pair recombination sites and the observed voltage signals are primarily due to a LIVA effect.

Den diskursive distribution af struktur og agens

Marianne Winther Jørgensen: The discursive distribution of structure and agency. An ana-lysis of subject positions in the human sciences One of the central issues in sociology is the relation between structure and agency. While there have been many discussions and proposals about the relationship between them, none has been accepted as a final answer. This article explores that issue employing Foucault’s diagnosis of modern man, and suggests that the question of structure and agency is posed in a way that precludes such an answer. This does not, however, render all discussion obsolete, but rather leaves space for a perspective on the discursive construction and distribution of structure and agency. Two texts are examined, one by Bourdieu and one by Tyler. Both have a similar objective – employing texts in a way to further agency, but these authors see their own role differently. Bourdieu gives himself and science a privileged position as regards access to knowledge, while Tyler sees structures as agents and himself as deliverer, that is, spokesperson for an inevitable development. The author proposes conceiving agency as an “empty form“ and argues that there is a need for agency in order to discuss responsibility and to localize potential for change.

Osteopontin is a ligand for the alpha4beta1 integrin

Recent work has shown that osteopontin expression is upregulated at sites of cardiovascular injury. It has been hypothesized that osteopontin provides an adhesive matrix for endothelial and smooth muscle cells during remodeling of the vascular wall following injury. Osteopontin has also been found to be synthesized by monocytes and macrophages within injury sites. Here, we present data showing that osteopontin can promote leukocyte adhesion through the alpha4beta1 integrin. In the presence of physiologic concentrations of Mg2+ and Ca2+, osteopontin purified from bovine milk promoted cell-substrate adhesion of HL-60 and Ramos cells, two model leukocyte cell lines. As with other adhesive ligands, adhesion to osteopontin required leukocyte activation. Under these conditions, no adhesion to control substrates such as bovine serum albumin was observed. Leukocyte adhesion was inhibited by anti-integrin antibodies directed at either the alpha4 or beta1 integrin subunits but not by control antibodies directed to other integrins. Further adhesion experiments revealed that leukocyte binding to osteopontin was completely inhibited by an alpha4beta1-binding peptide containing the leucine-aspartate-valine (LDV) sequence, while a control, non-binding peptide containing leucine-glutamate-valine (LEV) had minimal effects. Affinity chromatography using either surface labeled HL-60 or Ramos cell extracts revealed that the alpha4beta1 integrin specifically bound to osteopontin. Immunoprecipitation of eluted fractions from these columns positively identified the alpha4beta1 integrin. In order to localize potential alpha4beta1-binding sites within osteopontin, the protein was proteolytically cleaved with thrombin. A 30 kDa N-terminal osteopontin fragment purified using fast protein liquid chromatography promoted alpha4beta1 dependent leukocyte adhesion in a manner similar to that of the intact protein. These data collectively demonstrate that the alpha4beta1 integrin is a new adhesion receptor for osteopontin and that an alpha4beta1 binding site exists in the NH2-terminal thrombin fragment of osteopontin.

Disulphide arrangement in bovine caseins: localization of intrachain disulphide bridges in monomers of κ- and αs2-casein from bovine milk

SummaryNaturally occurring monomeric κ-casein and αs2-casein in bovine milk were purified by ion-exchange chromatography in order to localize potential intrachain disulphide bridges. Enzymic cleavage of the proteins followed by mass spectrometry and amino acid sequence analysis of cystine-containing peptides revealed the presence of an intrachain disulphide bond in both proteins.